The ADARAI utility prepares the recovery log (RLOG), lists the information contained in the RLOG, creates the job control statements to recover the database, and disables ADARAI logging.
"Transaction" recovery is provided whenever an Adabas session is abnormally terminated. The Adabas autobackout routine, which is automatically invoked at the beginning of every Adabas session, removes the effects of all interrupted transactions from the database. See the restart/recovery information in the Adabas Operations documentation.
However, when a database dataset (ASSO, DATA, or WORK) is destroyed, it is necessary to restore and regenerate the database to recover the lost data.
The Adabas Recovery Aid utility ADARAI can be used to automate and optimize "database" recovery. It records and reports all information needed to recover the database and builds the recovery job stream (JCL/JCS), which is the basis for reexecuting the jobs performed from the time of the last SAVE to the point of failure and error.
Note:
The job stream generation function is not yet available under VSE/ESA
or VM/ESA.
The Adabas Recovery Aid comprises two components:
an interface (ADARAC) to collect information as relevant events occur against the database; and
a utility (ADARAI) to list the information collected, generate jobs to recover the database or files on the database, or deactivate recovery logging.
The collection interface is called by the nucleus and by all utilities to record information about each event that occurs; for example, a nucleus stop/start, a utility execution, or an event generated by the Adabas Online System.
The interface records all event information into a recovery log file (RLOG) for use by the utility component. The RLOG stores the information about datasets, utility parameters, and protection logs needed to build the recovery job control. The RLOG dataset is DD/RLOGR1.
In a nucleus cluster environment, all nuclei use the same RLOG. Concurrent updates to the RLOG are controlled by a lock.
Notes:
Information is stored on the RLOG by generation, the logical unit used for recovery.
A "generation" includes all activity between consecutive operations of
ADASAV SAVE/RESTORE (database),
RESTORE GCB, and/or
SAVE DELTA/RESTORE DELTA (database).
The first generation includes the first operation and extends to (but excludes) the second. A new generation is started when a database can be recovered in full after the previous operation.
Generations may be normal, restricted, or erroneous:
A generation is labelled "normal" if a full save was available when it started and no unusual events occurred while activities were being logged in it.
A generation is labelled "restricted" when certain events occur during the logging cycle that make it impossible for ADARAI to rebuild the database without user intervention. ADARAI generates a job, but the job will not run without help from the user. For example, if the Work dataset is decreased in size, the user must create a Work dataset with the original size so that the recovery job can run correctly up to the point where the Work dataset size was decreased.
A generation is labelled "erroneous" when errors occur during the logging cycle, for whatever reason. ADARAI generates a job, but the job will not run without changes.
Note:
When a generation becomes restricted or erroneous, Software AG
recommends that you start a new generation as soon as possible by performing an
on- or off-line save of the database. If the Delta Save Facility is installed,
a SAVE DELTA will start a new generation.
Noncurrent generations provide a history of operations that have affected the database for use in problem resolution or for audit purposes.
Access to noncurrent generations is essential if an attempt to recover a database fails after the RESTORE step in the recovery job is executed. At this point, the generation being recovered becomes the current generation. If it then becomes necessary to rebuild the recovery job, the generation being recovered will be an older generation.
The RLOG retains the number of generations specified by the MINGENS parameter during the ADARAI PREPARE step. ADARAI recycles generations when the number stored on the RLOG reaches the number specified by the MINGENS parameter.
When a new generation plus those already stored exceed the available RLOG space, one of two events will occur:
if the minimum number of generations as specified by MINGENS can be maintained, the oldest generation is overwritten; otherwise
the RLOG is placed "out of service" by setting a flag in the RLOG control block. In this case, data is no longer logged.
